This invention relates to the direct connection of ancillary equipment such as fascimile transceivers to the telephone network.
In many instances, it is necessary for various types of ancillary equipment including data terminals and facsimile transceivers to be directly connected to the switched telephone network, as contrasted with acoustic coupling, in order to satisfy certain wide band communication channel requirements. Heretofore, the telephone companies have offered various protective interface devices so as to permit the direct connection of ancillary equipment to the telephone network without any risk of harm to the network. Recently, the FCC has promulgated rules which will permit the direct connection of ancillary equipment to the telephone network without the use of the protective devices offered by the telephone companies if ancillary equipment or associated protective cicuitry satisfies certain requirements which are the subject of an FCC registration program.
The direct connection of ancillary equipment subject to the FCC rules will present a number of problems to the users of this ancillary equipment who wish to avoid, to the extent possible, the use of telephone company supplied equipment. For example, the network protective devices presently offered by the telephone company, commonly referred to as DAA (direct access arrangements), are typically supplied in conjunction with a telephone station set having an exclusion key. The exclusion key which is associated with the cradle of the telephone set is provided to assure that return of the telephone handset to the cradle will break the telephone line connection thus excluding the ancillary equipment from connection to the telephone network and thereby assuring that the telephone set will be prepared to receive the next incoming call. In the absence of such exclusion key, it is possible to maintain a telephone line connection even though the handset is returned to the cradle if one should forget to turn the data access arrangement off so as to break the telephone line connection. On the other hand, it is desirable to utilize certain telephone company supply equipment such as, for example, a "500" type telephone set in conjunction with the ancillary equipment so as to provide a voice communication and dialing capability. Thus it is desirable to provide the exclusion function normally provided by the exclusion key in conjunction with the standard telephone set without such an exclusion key while at the same time maintaining the necessary isolation of the telephone network from the ancillary equipment.
Pori U.S. Pat. No. 3,886,314 discloses the direct connection of ancillary equipment and a telephone handset to the telephone network through an exclusion unit and coupler. The nature of the exclusion unit and coupler is not disclosed. Lee U.S. Pat. No. 3,822,364 and Gonsewski et al U.S. Pat. No. 3,524,935 disclose the connection of telephone station sets and ancillary equipment to the telephone network through coupling circuitry. Both patents disclose mode selection arrangements for the transfer of the primary communication connection from the telephone set to the ancillary equipment.